1. Field of the Invention
The present invention relates in general to a two-axis ball-based cursor control apparatus, such as a mouse or trackball, and in particular to a cursor control apparatus which provides the user with tactile feedback corresponding to uniform incremental movements of the cursor about both axes of movement.
2. Background Art
Two-axis cursor control devices are well-known in the art. These types of devices are common components of personal computer systems used for controlling the movement of a cursor appearing on a video monitor. Cursor control devices are also finding use in handheld devices such as PDA""s and cellular telephones where graphical user interfaces are manipulated by the user. Two well-known forms of such devices include the computer mouse and the trackball. A computer mouse consists of a spherical ball, approximately one-half inch in diameter and freely rotatable about two axes of rotation, mounted within a larger housing which rests on a flat surface, so that a portion of the ball protrudes from the bottom of the housing and comes into contact with the surface. Typically, a pair of rotors are positioned in contact with the ball, one aligned with each axis. Each of these rotors are in turn connected by an axle to a disk with uniformly spaced slots or holes around the outer portion thereof When the mouse is moved along the flat surface, the rotation of the ball is translated to the rotors, and in turn to the associated disks. Light emitters and sensors are positioned spanning each of the disks whereby the beam of light is alternatively passed through the disk to the sensors and then blocked from the sensors as the disk rotates. Each disk typically has two pairs of emitters and sensors associated therewith in order to determine the rate and direction of rotation of the disk. The sensors are connected to an electrical circuit which generates an electrical signal. From the signals generated by each of the two disks positioned perpendicular to one another, the direction and acceleration of the displacement of the ball, and hence of the mouse itself, is determined. This information is then translated into motion of the cursor on the screen of the computer using a predetermined relationship between the magnitude of the mouse displacement in each direction and the distance which the cursor moves in that direction. Thus, the user""s horizontal and vertical movement of the mouse on the flat surface is translated into horizontal and vertical movement of the cursor on the screen.
A trackball is a similar type of cursor control apparatus in which the user merely rotates the ball itself instead of moving the entire housing. The ball typically protrudes from the top of its housing, where it can be rotated directly by the user by hand. The remainder of the device is typically substantially similar to that described above, with the rotation of the ball translated to a pair of rotors associated with each axis of rotation, and then to a pair of disks, whose motion is then translated into cursor motion by light sensors. Thus, unlike a mouse, a trackball apparatus remains stationary while the user directly rotates the ball itself.
There are, however, certain disadvantages to these types of cursor control devices. In order to achieve precise targeting of the cursor, the user must possess a certain degree of hand to eye coordination to align the cursor with the desired location. This can be troublesome in certain applications, such as pull-down menus implemented in PC graphical user interface based operating systems. Typically a single mouse click causes a number of further commands or options to appear in row after row. To select a give command or option the user must position the cursor over the text label for the desired option to execute same. Any slight movement of the device by the user will cause the cursor displayed on the screen to move to a different command or option item than that desired. Positioning is accomplished by moving the mouse or trackball, which moves in one continuous motion, until the cursor is in position. The absence of any tactile feedback corresponding to the movement of the cursor makes such precise targeting even more difficult. In addition, some devices have a tendency for the cursor to drift from its desired location because any slight or unintentional force exerted on the control device will cause it to move, and correspondingly displace the cursor from the desired location. In applications where precise targeting and control of the cursor is essential, for instance in computer aided drafting, these drawbacks are particularly unwelcome. Incorporating graphical user interfaces into smaller devices, such as cellular phones, causes potential safety issues. For example, a person using a phone in a car to recall a speed dial number using the graphical interface may cause an accident by trying to align a cursor over the display of names or numbers stored in memory.
Also known in the prior art are control devices consisting of a rotatable disk or wheel which is rotatable about only one axis in discrete, uniform increments. Examples of such devices include dials for applications such as frame-by-frame movement in a video-disc player or to switch tracks on an audio-disc player. Such devices may provide tactile feedback to the user in the form of a xe2x80x9cclickingxe2x80x9d or ratcheting effect which occurs when the disk or wheel is rotated. The user knows when such a device has advanced from one position to the next because of the tactile sensation triggered by the dial xe2x80x9csnappingxe2x80x9d into the next position. Such known devices, however, have the disadvantage of providing such incremental rotation about only one axis, therefore making them ill-suited for applications requiring control of a cursor moving in two dimensions.
It would therefore be desirable to provide a cursor control device which would allow the user to move the cursor in discrete, uniform increments in two dimensions, in order to more easily achieve precise targeting of the cursor with its intended position on the screen. Further, it would also be desirable to provide for such a device which provides tactile feedback to the user which corresponds to the movement of the cursor on the screen. In addition, it would be desirable to provide for such a device in which the unintentional motion of the cursor due to inadvertent movement of the device is minimized.
These and other objects of the present invention will become apparent to those of ordinary skill in the art in light of the present specifications, drawings, and claims.
The present invention is directed to a two-axis ball-based cursor control apparatus providing for discrete, uniform displacements in each direction of rotation in order to achieve a precise alignment of cursor and target in electronic displays, and also providing for tactile feedback corresponding to each incremental displacement. The cursor control apparatus comprises a housing, a spherical ball partially within said housing capable of freely rotating about at least two axes, a plurality of first magnetic elements within the spherical ball securely positioned relative to one another, and a plurality of second magnetic elements fixed within the housing. The second magnetic elements are positioned so that, when the spherical ball is at rest, an attractive magnetic force exists between one or more of the first magnetic elements and one or more of the second magnetic elements, in order to maintain the spherical ball at rest until a rotational force greater than the attractive force is applied to it by the user. When such a force is applied, the ball rotates about at least one axis until such time as the applied force no longer exceeds the attractive force, at which time the attractive force causes the spherical ball to come to a stop at a new stationary position. This provides the user with tactile feedback indicating that the position of the spherical ball has changed.
In one embodiment, each of the first magnetic elements is composed of a magnetically responsive material, such as ferrous metal, and each of the second magnetic elements is composed of a permanent magnet or electromagnet. It is deemed within the scope of the present invention to utilize any material or combination of materials provided that they are attracted to one another by magnetic force. In a second embodiment, each of the first magnetic elements is composed of a permanent magnet and each of the second magnetic elements is composed of a magnetically responsive material, such as a ferrous metal. In a third embodiment, each of the first magnetic elements and each of the second magnetic elements are composed of permanent magnets, with the first and second elements positioned so that when a first magnetic element and a second magnetic element come into close proximity with one another, the ends of each which are nearest to one another are of opposite polarity, thereby attracting one to the other.
In a preferred embodiment, the cursor control apparatus also comprises a means for measuring the displacement of the spherical ball about each axis of rotation. This may comprise a plurality of rotors adjacent to the spherical ball, and an axle and a rotating disk associated with each rotor. The rotors are positioned so as to transfer the rotational motion of the spherical ball about one axis of rotation to the corresponding rotating disk. This embodiment also comprises at least one electronic sensor associated with each rotating disk for measuring the direction and magnitude of the rotation of the rotating disks and for providing a signal to the associated electronic device, which changes the position of the cursor.
In another embodiment of the invention, the spherical ball further comprises a stabilizer which provides an additional force to maintain the spherical ball in a stationary position. This stabilizer may comprise an arm extending from said housing and a rotor attached to the arm which is positioned so as to exert a force on the surface of the spherical ball biasing the ball toward the two rotors.
A further embodiment includes a plurality of pivoting members within the spherical ball, each of which contains one of the first magnetic elements. The pivoting members are allowed to pivot in order to maintain a uniform separation between the first magnetic elements and the second magnetic elements when the spherical ball is stationary.
In another embodiment, the invention further comprises at least one switch element for allowing the user to select options corresponding to particular cursor locations on an electronic display screen. This at least one switch element may comprise at least one button element which is manipulated directly by pressure applied thereto by the user in order to trigger the switch element. The at least one switch element may also be positioned so as to come into contact with the spherical ball when pressure is applied to the spherical ball by the user, causing the spherical ball to depress the switch element, thereby triggering the switch element.
In the event that an electromagnet is utilized, the user may be provided with the option of disconnecting the power to the electromagnet such that the present device can operate as a conventional cursor control apparatus providing for continuous movement and reconnecting the power to operate the present apparatus with tactile feedback.